On Thu, Oct 23, 2008 at 7:21 AM, Raindog wrote:

I ran into a problem while cleaning up some old code. What I wanted to do was replace explicit for loops with some stl algorithms or BOOST_FOREACH. Below is the original function:

|//in header file: ..snip typedef std::vector chunk_vec_t chunk_vec_t chunks; ..snip

//in source file: uint32_t ADT::get_connectivity_data( std::vector< std::vector > &output ) { output.resize(chunks.size()); for(chunk_vec_t::iterator it = chunks.begin(); it < chunks.end(); ++it) { uint32_t success = (*it)->get_connectivity_data(output[it-chunks.begin()]); } return TRUE; }

I asked on a separate website for some possibilities of replacing this code with boost::lambda, and the following almost correct suggestion was given to replace the loop:

||std::for_each( chunks.begin(), chunks.end(), bind( &chunk_vec_t::value::type::get_connectivity_data, _1, output[ std::distance( _1, chunks.begn() ] ) );

The problem is that the above obviously does not compile, so I made some changes and came up with this:

||std::for_each( chunks.begin(), chunks.end(), bind( &chunk_vec_t::value_type::StoredType::get_connectivity_data, _1, output[ std::distance( &_1, &chunks[0] ) ] ) );

The problem with the above is that "||&chunk_vec_t::value_type::StoredType::get_connectivity_data|" causes the VC9 compiler to crash =(

So I made this change:

|std::for_each( chunks.begin(), chunks.end(), bind( &ADTChunk::get_connectivity_data, _1, output[ std::distance( _1, chunks.begin() ) ] ) );

But now I get an error with the call to std::distance not being able to discern the arguments due to ambiguity.

Next I thought that I might be able to use zip_iterator to assist in dealing with both of the containers, and then I realized it used tuples, which then made me thing that extracting the iterators from the tuples is going to take a lot of boiler plate code itself. Which led me to settle with the following code that is concise and easily readable but will only work if chunks is a vector essentially:

BOOST_FOREACH(chunk_vec_t::value_type it, chunks) { output[std::distance(&it, &chunks[0])] = it->get_connectivity_data(); }

So, my final question is, given my above attempts, is there a way to do what the 1st and 5th(the one immediately above this line) code snippets do in a straight-forward manner using either boost::lambda, or, since it will be replaced eventually by phoenix v3, with phoenix v2?

I confess to having only given this a cursory glance over the first coffee of the day, but isn't this essentially a transform operation, for which the transform algorithm would be the clearest solution? Cheers, Rob.